Implemented Command Factory such that commands can be implemented as
separate Command classes and registered at the CommandFactory.
Remove redundant .intValue() call.
Implemented /mode command for making mode changes. (Querying mode is not
supported yet.)
Modified /nick to use IdentityManager for nick changing.
Fine-tuned implementation for Msg and Nick command and unit tests.
Fine-tuned /me command and added unit tests.
Fine-tuned commands Mode, Join + added unit tests.
Improved CommandFactory implementation.